<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 一些常用的背景相关小属性可以合写  【color image repeat position】 */
        /* background:white url(1.png) no-repeat center center */ 
        /* 属性合写非常非常常用 */
        div{
            width: 300px;
            height: 300px;
            border: 1px solid #000;
            background: yellow url(3.png) no-repeat center center;
            background-size:100px auto; 
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>